1. Field of the Invention
The invention is related to the field of electromagnetic clutches and, in particular, to an electromagnetic fan clutch which may be bolted to an existing fan drive hub associated with an internal combustion engine.
2. Description of the Prior Art
Electromagnetic fan clutches for internal combustion engines of the type taught by Pierce in U.S. Pat. No. 2,796,962 and more recently by Mower in U.S. Pat. Nos. 4,119,184 and 4,278,161 have found wide acceptance, particularly in the trucking industry. As is known, automotive radiator fans can consume considerable power, especially at high road speeds, where the augmentation of the air flow through the engine's radiator is usually not necessary for adequate engine cooling. Therefore, electromagnetic fan clutches which are capable of disconnecting the fan from the engine's fan drive whenever the engine is cold or being adequately cooled by the air being ducted through the radiator at nominal to high speed driving conditions could eliminate this waste of engine power. Up until recently, the fuel savings realized by disconnecting the fan from the fan drive when not needed did not justify the cost of these electromagnetic fan clutches. However, with the increase in the price of fuel, this condition no longer exists and now the use of electromagnetic clutches controlling the operation of the radiator fan is economically justifiable. A considerable market now exists for retrofitting vehicles, especially trucks with electromagnetic fan clutches which are controlled by sensors detecting the temperature of the engine and/or its coolant.
The problem with the fan clutches taught by Mower et al is that due to the limited space between the fan drive hub and the radiator, the solenoid coil housing is located adjacent to the flange which mounts to the fan drive hub of the internal combustion engine. The space between the flange and the solenoid coil housing is too small to permit the insertion of bolts which secure the flange to the fan drive hub. These fan clutches come in kit form, in which the fan clutch assembly is disassembled. This permits the flange to be bolted to the fan drive before the solenoid coil housing is connected on the shaft. In the mounting of this type of fan clutch the individual component of the clutch must be mounted on the fan drive in a predetermined sequence. The invention is an improved version of the electromagnetic fan clutch of the type taught by Mower et al which is pre-assembled at the factory and only needs to be bolted to the engine's fan drive hub.